Magnetic sensor with a chamfered magnetic body facing a magnetoresistive element

ABSTRACT

A magnetic sensor according to the invention has a magnetoresistive element having a multi-layer structure and a magnetically sensitive axis, and at least a soft magnetic body that is arranged near the magnetoresistive element. The soft magnetic body has a sloping line at least at a corner thereof, wherein the sloping line is tilted with respect to two sides of the soft magnetic body that extend to the corner, as viewed in a stacking direction of the magnetoresistive element.

BACKGROUND OF THE INVENTION Field of the Invention

The present application is based on, and claims priority from, JPApplication No. 2017-250476, filed on Dec. 27, 2017, the disclosure ofwhich is hereby incorporated by reference herein in its entirety.

The present invention relates to a magnetic sensor.

Description of the Related Art

As a sensor for detecting the position of a moving object, a magneticsensor that has an element having a magnetoresistive effect is known(see JPH11-87804). A magnetic sensor moves relative to a magnet andthereby detects a change in an external magnetic field that is generatedby the magnet, and calculates the moving distance of the moving objectbased on the change in the external magnetic field that is detected.

The magnetic sensor disclosed in JPH11-87804 has a giantmagnetoresistive thin film having a magnetoresistive effect and a pairof soft magnetic thin films, as disclosed in FIG. 1 thereof. The giantmagnetoresistive thin film of this magnetic sensor is elongate, and thesoft magnetic thin films are arranged on both sides of the giantmagnetoresistive thin film with regard to the long axis thereof. Eachsoft magnetic thin film is rectangular, as viewed in the film thicknessdirection of the giant magnetoresistive thin film. In other words, everycorner of each soft magnetic thin film has an edge (a pointed part), asviewed in the film thickness direction of the giant magnetoresistivethin film. In this magnetic sensor, a giant magnetoresistive thin filmhaving poor sensitivity to a magnetic field is combined with softmagnetic thin films in order to enhance the sensitivity to a magneticfield.

SUMMARY OF THE INVENTION

In the magnetic sensor disclosed in JPH11-87804, in which the softmagnetic thin films are arranged on both sides of the giantmagnetoresistive thin film, a magnetic field that is directed in adirection other than the direction of the magnetically sensitive axis ofthe giant magnetoresistive thin film is considerably shielded. However,a magnetic sensor is desired that is improved in shielding performanceof a magnetic field that is directed in a direction other than thedirection of the magnetically sensitive axis.

The present invention aims at providing a magnetic sensor having a softmagnetic body that, when the magnetic body is used as a shield,effectively shields a magnetic field that is directed in a directionother than the direction of the magnetically sensitive axis and that,when the magnetic body is used as a yoke, has small hysteresis.

A magnetic sensor according to the present invention comprises: amagnetoresistive element having a multi-layer structure and amagnetically sensitive axis; and at least a soft magnetic body that isarranged near the magnetoresistive element. The soft magnetic body has asloping line at least at a corner thereof, wherein the sloping line istilted with respect to two sides of the soft magnetic body that extendto the corner, as viewed in a stacking direction of the magnetoresistiveelement.

According to the magnetic sensor of the present invention, when themagnetic body is used as a shield, the magnetic body effectively shieldsa magnetic field that is directed in a direction other than thedirection of the magnetically sensitive axis, and when the magnetic bodyis used as a yoke, the magnetic body has small hysteresis.

The above and other objects, features and advantages of the presentinvention will become apparent from the following descriptions withreference to the accompanying drawings which illustrate examples of thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of the main portion of a magnetic sensoraccording to a first embodiment;

FIG. 1B is a circuit diagram of the magnetic sensor according to thefirst embodiment;

FIG. 10 is a sectional view of an element portion that constitutes themain portion of the magnetic sensor according to the first embodiment;

FIG. 1D is an enlarged view of an end portion of the soft magnetic bodywith regard the long axis thereof, wherein the soft magnetic bodyconstitutes the magnetic sensor according to the first embodiment;

FIG. 2 is an enlarged view of an end portion of the soft magnetic bodywith regard the long axis thereof, wherein the soft magnetic bodyconstitutes a magnetic sensor according to a first comparativeembodiment;

FIG. 3A is a graph showing a relationship between a chamfering area anda shielding factor of a magnetic field in the X axis direction that iscaused by unnecessary magnetic domains;

FIG. 3B is a graph showing a relationship between the chamfering areaand the shielding factor of a magnetic field in the X axis direction,wherein the magnetic field is caused by the volume of an end portion ofa soft magnetic body with regard the long axis thereof;

FIG. 3C is a graph showing a relationship between the chamfering areaand a combined (that is, calculated from the graphs of FIGS. 3A and 3B)shielding factor of a magnetic field in the X axis direction;

FIG. 4 is a graph showing a transmittance rate of a magnetic field inthe X axis direction at different positions of the soft magnetic body inthe X axis direction in the first embodiment and in the firstcomparative example;

FIG. 5A is an enlarged view of an end portion of a soft magnetic bodywith regard the long axis thereof, wherein the soft magnetic bodyconstitutes a magnetic sensor according to the second embodiment;

FIG. 5B is an enlarged view of an end portion of a soft magnetic bodywith regard the long axis thereof in the first embodiment, illustratingmagnetic domains of a portion that the first embodiment has but thesecond embodiment does not have;

FIG. 6 is an enlarged view of an end portion of a soft magnetic bodywith regard to a direction parallel to long sides thereof, wherein thesoft magnetic body constitutes a magnetic sensor according to a thirdembodiment;

FIGS. 7A and 7B are a plan view and a side view of the main portion of amagnetic sensor according to a fourth embodiment, respectively;

FIG. 8A is a graph showing a relationship between a chamfering area anda hysteresis value;

FIG. 8B is a graph showing a relationship between a chamfering area anda Q-value (energy transforming efficiency);

FIG. 8C is a graph showing a relationship between a chamfering area anda Q-value/a hysteresis value;

FIGS. 9A and 9B are a plan view and a side view of the main portion of amagnetic sensor according to a fifth embodiment, respectively; and

FIGS. 10A to 10J are enlarged views of end portions of soft magneticbodies according to first to tenth modifications with regard to the longaxis thereof, respectively.

DETAILED DESCRIPTION OF EMBODIMENTS

Explanation will be given about first to fifth embodiments, as well asmodifications of the embodiments. In the following descriptions, “endportion” means “end portion with regard to the long axis thereof” unlessotherwise defined.

First Embodiment

Magnetic sensor 10 (see FIGS. 1A to 1D) of the present embodiment is,for example, a sensor for detecting a position of moving object (notshown) having a magnet, that is, a position sensor. Magnetic sensor 10of the present embodiment is configured to move relative to theabove-mentioned magnet and thereby to detect a change in an externalmagnetic field that is generated by the magnet, and to calculate themoving distance of the moving object based on the change in the externalmagnetic field that is detected. Magnetic sensor 10 of the presentembodiment has a magnetically sensitive axis, which is the Y axis (seeFIG. 1A etc.), described later, and detects a change in the magneticfield in the Y axis direction. In the following descriptions, the Z axisdirection (see FIG. 1A) corresponds to the stacking direction of eachelement portion 20, described later, and the X axis direction (see FIG.1A) corresponds to a direction that is perpendicular both to the Z axisdirection and to X axis direction.

Magnetic sensor 10 of the present embodiment is used, for example, for alens position detecting mechanism that constitutes an auto focusmechanism or an optical shake correction mechanism of a camera of amobile information terminal and the like.

Magnetic sensor 10 of the present embodiment has magnetoresistiveelement portion 100 that is constructed by a plurality of elementportions 20 (an example of a magnetoresistive element), a plurality ofupper shields 32 (an example of a soft magnetic body) and a plurality oflower shields 34 (another example of the soft magnetic body), as shownin FIGS. 1A and 1B. Upper shield 32 and lower shield 34 form a pair ofshields 30, as described later. A plurality of pairs of shields 30 isprovided, and the pairs of shields 30 are arranged in the X axisdirection in an orientation described later (see FIG. 1A).

As shown in FIG. 1B, magnetic sensor 10 of the present embodiment hassensor portion 200, in which magnetoresistive element portions 100 andresistor elements 110 are bridge-connected to each other, and integratedcircuit 300 having input terminal 310 that is electrically connected tosensor portion 200, ground terminal 320, differential amplifier 330 andexternal output terminal 340 etc.

Each element portion 20 of the present embodiment has a filmconfiguration in which films are stacked (an arrangement of stackedfilms), as described later (see FIG. 10). Here, the Z axis direction isan example of the stacking direction. Each element portion 20 has amagnetoresistive effect, described later.

In an example, a plurality of element portions 20 forms a group in whichelement portions 20 are arranged in the Y axis direction at apredetermined interval (see FIG. 1A). A plurality of the groups isprovided and the groups are arranged in the X axis direction at apredetermined interval. In each group that is formed of a plurality ofelement portions 20, element portions 20 that are adjacent to each otherare connected to each other by an electrode (not shown), and acombination of each group and each electrode forms a meander shape.Further, a combination of each group and each electrode is connected toanother combination that is adjacent to the former in the X axisdirection via an electrode (not shown). Accordingly, element portions 20of the present embodiment are connected in series by a plurality ofelectrodes.

The groups, each formed of a plurality of element portions 20, arearranged in the X axis direction at a predetermined interval in theembodiment, as described above, but may be arranged in a direction otherthan the X axis direction.

Each element portion 20 of the present embodiment has, for example, atypical spin-valve type film configuration, as shown in FIG. 10.Specifically, each element portion 20 includes free layer 151 whosemagnetization direction is changed depending on an external magneticfield, pinned layer 153 whose magnetization direction is pinned relativeto the external magnetic field, spacer layer 152 that is positionedbetween and that is in contact both with free layer 151 and with pinnedlayer 153, antiferromagnetic layer 154 that is adjacent to pinned layer153 on the back side thereof, as seen from spacer layer 152. Free layer151, spacer layer 152, pinned layer 153 and antiferromagnetic layer 154are stacked above a substrate (not shown). Antiferromagnetic layer 154fixes the magnetization direction of pinned layer 153 by the exchangecoupling with pinned layer 153. Pinned layer 153 may also have asynthetic structure in which two ferromagnetic layers sandwich anonmagnetic intermediate layer. Spacer layer 152 is a tunneling barrierlayer that is formed of a nonmagnetic insulator, such as Al₂O₃.Accordingly, each element portion 20 of the present embodiment is atunneling magnetoresistive element (a TMR element) having a tunnelingmagnetoresistive effect. A TMR element is advantageous in that it has alarger MR ratio and a larger output voltage from the bridge circuit thana GMR element.

A pair of shields 30 of the present embodiment is arranged near eachelement portion 20 and has a function of shielding a magnetic field inthe X axis direction (absorbing an external magnetic field that isapplied in the X axis direction). A pair of shields 30 consists of uppershield 32 that is arranged on the upper side of element portion 20 andlower shield 34 that is arranged on the lower side of element portion20, as shown in FIG. 1A. In one example, lower shield 34 has the sameshape as upper shield 32. Upper shield 32 and lower shield 34 areelongate and are arranged such that the long axis thereof extend in theY axis direction and former overlaps with the latter, as viewed in the Zaxis direction. In the present embodiment, the Y axis directioncorresponds to a direction of the long axes of upper shield 32 and lowershield 34, and the X axis direction corresponds to a direction of theshort axes of upper shield 32 and lower shield 34. Upper shield 32 andlower shield 34 are rectangular, as viewed in the Z axis direction.Upper shield 32 and lower shield 34 are arranged on the upper side andon the lower side of each group of element portions 20 that are arrangedin the Y axis direction, respectively, such that upper shield 32 andlower shield 34 sandwich each group of element portions 20. The pairs ofshields 30 sandwich the respective groups that are arranged in the Xaxis direction. Each upper shield 32 and lower shield 34 is formed, forexample, of NiFe, CoFe, CoFeSiB, CoZrNb and the like.

Accordingly, the pairs of shields 30 that are arranged in the X axisdirection absorb a magnetic field in the X axis direction in order toshield a magnetic field in the X axis direction that is applied to thearea where element portions 20 are arranged.

Next, referring to FIGS. 1A and 1D, explanation will be given about theshapes of both end portions 35 of upper shield 32 and lower shield 34 ofthe present embodiment. In the following descriptions, explanation willbe given on upper shield 32 because lower shield 34 has the same shapeas upper shield 32 and is formed of the same material as upper shield32, as described above. Regarding lower shield 34, refer to thefollowing explanation of upper shield 32. One of both end portions 35and the other are in line symmetry regarding an imaginary line thatextends in the X axis direction, as viewed in the Z axis direction.Thus, the illustration of the other of end portions 35 is omitted inFIG. 1D.

As described above, each upper shield 32 is rectangular, as viewed inthe Z axis direction (see FIG. 1A). Each upper shield 32 is shaped suchthat each corner 36, that is, four corners 36, is chamfered, as viewedin the Z axis direction. In the present descriptions, a shape withchamfering is referred to as a chamfered shape. In other words, eachcorner 36 of each upper shield 32 has a shape of so-called C-chamferingor 45° chamfering that looks as if it would be formed by removing apexportion 37 that originally existed (the isosceles triangle portion thatis defined by the dot-dash lines and the real line of corner 36 in FIG.1D. Also see FIG. 2.), as viewed in the Z axis direction. In otherwords, each upper shield 32 has a sloping line that is tilted withrespect to two sides 30X, 30Y (described later) of upper shield 32 thatextend to corner 36, as viewed in the Z axis direction. In the presentdescription, the sloping line may be used interchangeably with corner36, and the sloping line may be referred to as sloping line 36. Itshould be noted that each shield 32, 34 of the present embodiment hasthe same shape as each shield 32, 34, as viewed in the Z axis direction,at any section that is perpendicular to the Z axis direction.

Chamfering area S of apex portion 37, as viewed in the Z axis direction,is S1 (μm²) or more and S2 (μm²) or less. In the present embodiment, S1is 1.0×10⁻³, and S2 is 2.5×10. Chamfering area S is calculated in thefollowing manner. Suppose that the long side of upper shield 32 is side30Y (an example of an arbitrary line), a short side of upper shield 32is side 30X (an example of another line that is inclined relative to thearbitrary line) and an intersection of an extension of side 30Y and anextension of side 30X is intersection IS, as seen in the Z axisdirection in FIG. 1D. Here, “inclined relative to the arbitrary line”means “not parallel to the arbitrary line”. Further, suppose that animaginary line that is a part of the extension of side 30Y and thatconnects side 30Y to intersection IS is imaginary line 30YA. Supposethat an imaginary line that is a part of the extension of side 30X andthat connects side 30X to intersection IS is imaginary line 30XA.Suppose that the area of a region that is surrounded by imaginary line30YA, imaginary line 30XA and corner 36, as viewed in the Z axisdirection, is chamfering area S. As mentioned above, each shield 32, 34is octagonal with four corners 36 chamfered at angles of 45°, as viewedin the Z axis direction. Thus, each corner has angles of 135° or anobtuse angle, as viewed in the Z axis direction. Accordingly, eachshield 32, 34 of the present embodiment has a shape having an obtuseangle on at least a part of the circumference thereof, as viewed in theZ axis direction. It should be noted that side 30Y is an example of anarbitrary line and side 30X is an example of another line that isinclined relative to the arbitrary line in the embodiment, but side 30Xmay be an example of an arbitrary line and side 30Y may be an example ofanother line that is inclined relative to the arbitrary line. It shouldalso be noted that an arbitrary line is a long side and another line isa short side and vice versa in the embodiment, but other arrangementsare also possible. For example, both an arbitrary line and another linehave the same length.

Next, the effects of the present embodiment (the first and secondeffects) will be described with reference to the drawings. In theexplanation, the present embodiment will be compared to a firstcomparative example (See FIG. 2), as needed, and when the same elementsare used in the first comparative example as in the present embodiment,the names and reference numerals in the present embodiment will be used.

The first effect is obtained by the chamfered shape of at least onecorner 36 of upper shield 32 or lower shield 34 (see FIGS. 1A and 1D).The first effect will be explained by comparing the present embodimentto the first comparative example (See FIG. 2), described later. The sameelements in the first comparative example as in the present embodimentwill be referred to by the names and reference numerals in the presentembodiment.

In each shield 32A, 34A of magnetic sensor 10A of the first comparativeexample, any corner 36 is not chamfered and every corner 36 has apexportion 37 (See FIG. 2). Magnetic sensor 10A of the first comparativeexample is the same as magnetic sensor 10 of the present embodimentexcept for the above.

In magnetic sensor 10A of the first comparative example, unstablemagnetic field component Bx that is directed in the X axis directionoccurs at the edge of end portion 35, as shown in FIG. 2. In otherwords, magnetic domains are generated along a direction in which amagnetic field is to be shielded by each shield 32A, 34A. As a result,in magnetic sensor 10A of the first comparative example, the capabilityof shielding a magnetic field of each shield 32, 34 deteriorates due tothe unstable magnetic field component Bx.

In contrast, in each shield 32, 34 (see FIGS. 1A and 1D) of magneticsensor 10 of the present embodiment, each corner 36 is formed into achamfered shape that does not have a portion that correspond to apexportion 3, as compared to each shield 32A, 34A of the first comparativeexample (See FIG. 2). In other words, each shield 32, 34 of the presentembodiment does not have apex portion 37, as compared to each shield32A, 34A of the first comparative example.

Accordingly, in magnetic sensor 10 of the present embodiment, unstablemagnetic field component Bx that occurs in magnetic sensor 10A of thefirst comparative example does not occur or is less likely to occur. Asa results, magnetic sensor 10 of the present embodiment has highercapability of shielding a magnetic field in directions other than thedirection of the magnetically sensitive axis than magnetic sensor 10A ofthe first comparative example. In the present embodiment, each corner 36of each shield 32, 34 is chamfered. Thus, the present embodiment hashigher capability of shielding a magnetic field in directions other thanthe direction of the magnetically sensitive axis than an arrangement inwhich a part of corners 36 of each shield 32, 34 are chamfered but theother corners have apex portions 37.

The second effect is obtained by setting chamfering area S of corners 36of each shield 32, 34 to be S1 (μm²) or more and S2 (μm²) or less, asviewed in the Z axis direction. Here, S1 is 1.0×10⁻³, and S2 is 2.5×10.The second effect will be explained by comparing the present embodimentto second and third comparative examples (not shown), described later.The same elements that are used in the second and third comparativeexamples as used in the present embodiment will be referred to by thenames and reference numerals in the present embodiment.

The second comparative example is different from the present embodimentin that chamfering area S of each shield is less than S1 (μm²). Thethird comparative example is different from the present embodiment inthat chamfering area S of each shield is larger than S2 (μm²). Here, S1is 1.0×10⁻³, and S2 is 2.5×10. The magnetic sensors according to thesecond and third comparative examples have the same configuration asmagnetic sensor 10 of the present embodiment except for the above.

FIG. 3A is a graph showing a relationship between chamfering area S anda shielding factor of a magnetic field of each shield 32, 34 in the Xaxis direction (hereinafter referred to as a first shielding factor),wherein the magnetic field is caused by unnecessary magnetic domains(the regions that generate magnetic field component Bx, mentionedabove). As will be understood from the graph of FIG. 3A, the largerchamfering area S is, or to be more precise, the larger the volume ofchamfering area S as viewed in the Z axis direction is, or the largerthe area of the unnecessary magnetic domains (or to be more precise, thevolume of the unnecessary magnetic domains) is, the higher is the firstshielding factor. Here, the X axis direction corresponds to a directionin which a magnetic field is to be shielded in magnetic sensor 10 of thepresent embodiment.

In contrast, FIG. 3B is a graph showing a relationship betweenchamfering area S and a shielding factor of a magnetic field of eachshield 32, 34 in the X axis direction (hereinafter referred to as asecond shielding factor), which depends on the area of end portion 35 ofeach shield 32, 34 (as viewed in the Z axis direction). As will beunderstood from the graph of FIG. 3B, the larger chamfering area S is,or to be more precise, the larger the volume of chamfering area S asviewed in the Z axis direction is, the lower is the second shieldingfactor.

FIG. 3C is a graph showing a relationship between chamfering area S andthe first shielding factor and the second shielding factor. In otherwords, FIG. 3C is a combination of the graphs of FIGS. 3A and 3B,showing a relationship between chamfering area S and a shielding factorof a magnetic field in the X axis direction. Referring to FIG. 3C, theshielding factors of the first comparative example (See FIG. 2,chamfering area S=0), the second comparative example (chamfering areaS<S1) and the third comparative example (S2<chamfering area S) are lowerthan the shielding factor of the present embodiment (S1<=chamfering areaS<=S2). Here, S1 is 1.0×10⁻³, and S2 is 2.5×10.

Accordingly, magnetic sensor 10 of the present embodiment is capable ofmore effectively shielding a magnetic field in directions other than thedirection of the magnetically sensitive axis than the first to thirdcomparative examples.

FIG. 4 is a graph showing a simulation result of a transmittance rate ofa magnetic field at different positions of each shield 32, 34 in the Xaxis direction in the present embodiment (see FIG. 1D) and atransmittance rate of a magnetic field at different positions of a softmagnetic body in the X axis direction in the first comparative example(See FIG. 2). As will be understood from the graph of FIG. 4, thepresent embodiment shows a lower transmittance rate of a magnetic fieldat the center of the short side of each shield 32, 34 than the firstcomparative example. Accordingly, the present embodiment is capable ofmore effectively shielding a magnetic field in directions other than thedirection of the magnetically sensitive axis than the first comparativeexample. The inventor believes that this difference is cause byexistence/nonexistence and the size of the above-mentioned unnecessarymagnetic domains.

Second Embodiment

Next, referring to FIGS. 5A and 5B, magnetic sensor 10B of the secondembodiment will be explained. In the following descriptions, differencesbetween the present embodiment and the first embodiment will beexplained. When the same elements are used in the present embodiment asin the first embodiment, the names and reference numerals in the firstembodiment will be used.

As shown in FIG. 5A, in each shield 32B, 34B (another example of thesoft magnetic body) of magnetic sensor 10B of the present embodiment,connecting parts of corner 36 of the first embodiment that connectcorner 36 to long side 30Y and short side 30X and that is C-chamferedare R-chamfered (indicated by R in the figure) (see FIG. 1D). In otherwords, the circumference of corner 36 of the present embodiment isformed of a combination of a curved line that corresponds to aR-chamfered part and a straight line that corresponds to a C-chamferedpart, that is, a straight line and two curved lines that are connectedto both ends of the straight line, respectively, as viewed in the Z axisdirection. Since each shield 32B, 34B has the above-mentioned connectingparts along a part of the circumference, each shield 32B, 34B has acircumference that is at least partly formed of curved lines, as viewedin the Z axis direction. Magnetic sensor 10B of the present embodimenthas the same configuration as magnetic sensor 10 of the first embodimentexcept for the above.

FIG. 5B is an enlarged view of end portion 35 of each shield 32, 34 ofthe first embodiment, as viewed in the Z axis direction. In each shield32, 34 of the first embodiment, in which corner 36 is C-chamfered, sharpedges (magnetic domains) remain at the connecting parts that connectcorner 36 to long side 30Y and short side 30X. Such magnetic domains maycause unstable magnetic field component Bx.

In contrast, such magnetic field component Bx does not occur in thepresent embodiment because there is no sharp edge in corners 36, asdescribed above.

Accordingly, magnetic sensor 10B of the present embodiment is capable ofmore effectively shielding a magnetic field in directions other than thedirection of the magnetically sensitive axis than magnetic sensor 10Aaccording to the first embodiment.

Third Embodiment

Next, referring to FIG. 6, magnetic sensor 10C of a third embodimentwill be explained. In the following descriptions, differences betweenthe present embodiment and the first embodiment will be explained. Whenthe same elements are used in the present embodiment as in the firstembodiment, the names and reference numerals in the first embodimentwill be used.

In each shield 32C, 34C (another example of the soft magnetic body) ofmagnetic sensor 10C of the present embodiment, corners 36, which areC-chamfered in the first embodiment, are R-chamfered. In other words,the circumference of corners 36 of the present embodiment is formed ofcurved lines that correspond to R chamfering (indicated by arrows R), asviewed in the Z axis direction. Since each shield 32B, 34B has curvedlines that correspond to the above-mentioned R chamfering along a partof the circumference, each shield 32B, 34B has a circumference that isat least partly formed by curved lines, as viewed in the Z axisdirection. Magnetic sensor 10C of the present embodiment has the sameconfiguration as magnetic sensor 10 of the first embodiment except forthe above.

The present embodiment has the same effect as the first and secondembodiments.

Fourth Embodiment

Next, referring to FIGS. 7A and 7B, magnetic sensor 10D of the fourthembodiment will be explained. In the following descriptions, differencesbetween the present embodiment and the first embodiment will beexplained. When the same elements are used in the present embodiment asin the first embodiment, the names and reference numerals in the firstembodiment will be used.

Magnetic sensor 10D of the present embodiment has element portion 20 anda pair of yokes 30D (yoke 32D, 34D), as shown in FIGS. 7A and 7B. Eachyoke 32D, 34D (another example of the soft magnetic body) has the sameshape as upper shield 32 mentioned above (see FIGS. 1A and 1D) and isformed of the same material as upper shield 32 mentioned above. Eachyoke 32D, 34D is arranged in the Y axis direction such that the longaxis thereof is parallel to the Y axis direction and such that yokes32D, 34D sandwich element portion 20. The magnetically sensitive axis ofelement portion 20 is directed in the Y axis direction. In other words,element portion 20 of the present embodiment has a magneticallysensitive axis in a direction that crosses the Z axis direction, whichis the stacking direction thereof, or, more specifically, in a directionthat is substantially perpendicular to the Z axis direction. In thepresent embodiment, the Y axis direction corresponds to the long axis ofeach yoke 32D, 34D, and the X axis direction corresponds to a directionparallel to the short axis of each yoke 32D, 34D. Each yoke 32D, 34D ofthe present embodiment collects magnetic field in the Y axis directionand guides the magnetic field that is collected in the Y axis direction.Magnetic sensor 10D of the present embodiment has the same configurationas magnetic sensor 10 of the first embodiment except for the above. Aswill be understood from the above, each yoke 32D, 34D has an obtuseangle on at least a part of the circumference thereof, as viewed in theZ axis direction.

Next, the effect of the present embodiment will be described withreference to FIGS. 8A to 8C. The effect of the present embodiment isobtained by chamfering corners 36 of each yoke 32D, 34D, as viewed inthe Z axis direction, and by setting chamfering area S to be S1 (μm²) ormore and S2 (μm²) or less. Here, S1 is 1.0×10⁻³, and S2 is 2.5×10. Theeffect of the present embodiment will be explained by comparing thepresent embodiment to fourth to sixth comparative examples (not shown)described later. When the same elements are used in the presentembodiment as in the fourth to sixth comparative examples, the names andreference numerals in the present embodiment will be used.

In the fourth comparative example, each yoke is the same as each shield32A, 34A (See FIG. 2) of the first comparative example. In other words,the corners of each yoke of the fourth comparative example do not havechamfered shapes. The fifth comparative example is different from thepresent embodiment in that chamfering area S of each yoke is smallerthan S1 (μm²). The sixth comparative example is different from thepresent embodiment in that chamfering area S of each yoke is larger thanS2 (μm²). Here, S1 is 1.0×10⁻³, and S2 is 2.5×10. The magnetic sensorsaccording to the fourth to sixth comparative examples have the sameconfiguration as magnetic sensor 10D of the present embodiment exceptfor the above.

FIG. 8A is a graph showing a relationship between chamfering area S anda hysteresis value. In other words, the graph of FIG. 8A shows ahysteresis value that is caused by unnecessary magnetic domains. Thehysteresis value is a value that is proportional to an area of a regionthat is surrounded by a hysteresis curve. The smaller a hysteresis valueis, the better is the performance of a magnetic sensor. As shown in thegraph of FIG. 8A, the smaller chamfering area S is, the larger is thehysteresis value. The inventor believes that this is because unstablemagnetic field component Bx (See FIG. 2) that is caused by theunnecessary magnetic domains easily occurs as chamfering area S becomessmall.

FIG. 8B is a graph showing a relationship between chamfering area S andenergy transforming efficiency (a Q-value) of a magnetic field that iscollected by each yoke. As seen in the graph of FIG. 8B, the largerchamfering area S is, or the smaller the area of end portion 35, thelower is the Q-value.

FIG. 8C is a graph showing a relationship between chamfering area S andthe Q-value/the hysteresis value. As will be found from FIG. 8C, theQ-value/the hysteresis value of the fourth comparative example(chamfering area S=0), the Q-value/the hysteresis value of the fifthcomparative example (chamfering area S<S1) and the Q-value/thehysteresis value of the sixth comparative example (S2<chamfering area S)are smaller than the Q-value/the hysteresis value of the presentembodiment (S1<=chamfering area S<=S2). Here, S1 is 1.0×10⁻³, and S2 is2.5×10.

Accordingly, magnetic sensor 10D of the fourth embodiment is capable ofreducing a hysteresis value, while keeping a Q-value, as compared to thefourth to sixth comparative examples. As a result, magnetic sensor 10Dof the present embodiment is capable of enhancing linearity of thehysteresis curve while keeping a Q-value.

<Modification of the Fourth Embodiment>

Each yoke 32D, 34D of the present embodiment has the same shape as theshield of the first embodiment, as described above, but may have thesame shape as the shield of the second embodiment (see FIG. 5A) or thethird embodiment (see FIG. 6). End portion 35 of each yoke of themodification has a shape as shown in FIG. 5A (the circumference ofcorner 36 is formed of a combination of curved lines and a straightline, as viewed in the Z axis direction) or a shape as shown in FIG. 6(the circumference of corner 36 is formed of a curved line, as viewed inthe Z axis direction). Therefore, unstable magnetic field component Bx(see FIG. 5B) that is caused by the unnecessary magnetic domains is lesslikely to occur.

Accordingly, the modification of the fourth embodiment is capable offurther limiting a hysteresis value, as compared to the fourthembodiment. As a result, the modification of the fourth embodiment iscapable of further enhancing the linearity of the hysteresis curve.

Fifth Embodiment

Next, referring to FIGS. 9A and 9B, magnetic sensor 10E of the fifthembodiment will be explained. In the following descriptions, differencesbetween the present embodiment and the fourth embodiment will beexplained. When the same elements are used in the present embodiment asin the fourth embodiment, the names and reference numerals in the fourthembodiment will be used.

Magnetic sensor 10E of the present embodiment has element portion 20 anda pair of yokes 30E (yokes 32E, 34E), as shown in FIGS. 9A and 9B. Eachyoke 32E, 34E (another example of the soft magnetic body) is formed ofthe same material as above-mentioned upper shield 32 (see FIGS. 1A and1D). Each yoke 32E, 34E is a cuboid that is square with four cornerschamfered, as viewed in the Z axis direction, and that is rectangularwith long axis extending in the Z axis direction, as viewed in the Xaxis direction or in the Y axis direction. Yoke 34E is arranged at apredetermined position downstream of yoke 32E both in the X axisdirection and in the Y axis direction, as viewed in the Z axis direction(see FIG. 9A). Yokes 32E, 34E sandwich element portion 20, as viewed inthe Z axis direction. The magnetically sensitive axis of element portion20 is directed in the Y axis direction. Yoke 32E is arranged on theupper side of element portion 20 with regard to the Z axis direction andyoke 34E is arranged on the lower side of element portion 20 with regardto the Z axis direction, as viewed in the X axis direction (see FIG.9B). Each yoke 32E, 34E of the present embodiment collects a magneticfield in the Z axis direction and guides the magnetic field that iscollected in the Y axis direction. Magnetic sensor 10E of the presentembodiment has the same configuration as magnetic sensor 10D of thefourth embodiment except for the above.

As will be understood from the above, each yoke 32D, 34D has an obtuseangle on at least a part of the circumference thereof, as viewed in theZ axis direction. In the present embodiment, it is also possible to formcorners 36 into the shape of the second embodiment (see FIG. 5A) or thethird embodiment (see FIG. 6) (modification of the fifth embodiment) inthe same manner as the fourth embodiment is modified.

The present embodiment has the same effect as the fourth embodiment.

The present invention has been described by using the embodiments (firstto fifth embodiments and the modifications), but the present inventionis not limited to these. For example, the following embodiments(modifications) are also included in the scope of the present invention.

For example, in each embodiment, upper shield 32 and lower shield 34shield a magnetic field in the X axis direction, that is, in a directionof the short sides thereof. However, upper shield 32 and lower shield 34may shield a magnetic field in the Y axis direction, that is, in adirection of the long sides thereof, and it is needless to say that sucha configuration is also included in the scope of the present invention.

Further, corners 36 of each shield 32, 32 are C-chamfered in the firstembodiment (see FIG. 1D), and corners 36 of each shield 32A, 34A areC-chamfered and further R-chamfered at both ends thereof in the secondembodiment (see FIG. 5A). However, end portion 35 may be formed into ashape that is different from the shape of each embodiment as long as theabove-mentioned effect is obtained by removing unnecessary magneticdomains at end portion 35. For example, as shown in FIG. 10A, shield 32Faccording to a first modification may have end portion 35 that isR-chamfered along the entire width of the short side, as viewed in the Zaxis direction. Shield 32F according to the first modification has achamfered corner, as viewed in the Z axis direction, and has acircumference that is at least partly formed of a curved line, as viewedin the Z axis direction.

Further, as shown in FIG. 10B, each corner 36 of shield 32G according toa second modification may be formed such that there is not short side30X disappears (or almost disappears), as viewed in the Z axisdirection. Shield 32G according to the second modification has achamfered corner, as viewed in the Z axis direction, and has an obtuseangle on at least a part of the circumference thereof, as viewed in theZ axis direction.

Further, as shown in FIG. 100, shield 32H according to a thirdmodification may have a chamfered part that is formed only of a curvedline (a curve having an inflection point in this modification), asviewed in the Z axis direction. Shield 32H according to the thirdmodification has a chamfered corner, as viewed in the Z axis direction,and has a circumference that is at least partly formed of a curved line,as viewed in the Z axis direction.

Further, as shown in FIG. 10D, shield 32I according to a fourthmodification may have at least one corner that is not chamfered (thathas apex portion 37) and at least one chamfered corner, as viewed in theZ axis direction. Shield 32I according to the fourth modification has atleast one chamfered corner, as viewed in the Z axis direction, and has acircumference that is at least partly formed of a curved line, as viewedin the Z axis direction.

Further, as shown in FIG. 10E, shield 32J according to the fifthmodification may be chamfered into a rhombic shape such that short sides30X and long sides 30Y in the first embodiment disappear, as viewed inthe Z axis direction. Shield 32J according to the fifth modification hasa chamfered corner, as viewed in the Z axis direction, and has an obtuseangle on at least a part of the circumference thereof, as viewed in theZ axis direction. It should be noted that chamfering area S of thismodification is defined to be an area of the region that is surroundedby a rectangular that passes through each corner, or the rectangularthat is depicted with the dot-dash line in the figure, and shield 32J.

Further, as shown in FIG. 10F, shield 32K according to a sixthmodification may be chamfered into a parallelogram such that short sides30X in the first embodiment disappear, as viewed in the Z axisdirection. Shield 32K according to the sixth modification has achamfered corner, as viewed in the Z axis direction, and has an obtuseangle on at least a part of the circumference thereof, as viewed in theZ axis direction. It should be noted that chamfering area S of thismodification is defined to be an area of the region that is surroundedby a rectangular that is formed by the lines that extend from one end tothe other end of shield 32K in the Y axis direction and the lines thatextend from one end to the other end of shield 32K in the X axisdirection, or the rectangular that is depicted with the dot-dash line inthe figure and shield 32K.

Further, as shown in FIG. 10G, shield 32L according to a seventhmodification may be chamfered into a trapezoid such that short sides 30Xin the first embodiment disappear, as viewed in the Z axis direction.Shield 32L according to the seventh modification has a chamfered corner,as viewed in the Z axis direction, and has an obtuse angle on at least apart of the circumference thereof, as viewed in the Z axis direction. Itshould be noted that chamfering area S of this modification is definedto be an area of the region that is surrounded by a rectangular that isformed by the lines (the line of the longer side) that extend from oneend to the other end of shield 32K in the Y axis direction and the lines(the line in the height direction) that extend from one end to the otherend of shield 32K in the X axis direction, or the rectangular that isdepicted with the dot-dash line in the figure and shield 32L.

Further, as shown in FIG. 10I, shield 32M according to an eighthmodification may be chamfered into an ellipse such that short sides 30Xand long sides 30Y in the first embodiment disappear, as viewed in the Zaxis direction. Shield 32M according to the eighth modification has achamfered corner, as viewed in the Z axis direction, and has acircumference that is at least partly formed of a curved line, as viewedin the Z axis direction. It should be noted that chamfering area S ofthis modification is defined to be an area of the region that issurrounded by a rectangular that is defined by the major axis and minoraxis of shield 32M, or the rectangular that is depicted with thedot-dash line in the figure and shield 32M.

In each embodiment and each modification, each shield is elongate.However, the shield may have a shape other than an elongate shape aslong as the above-mentioned effect is obtained by removing unnecessarymagnetic domains at the end portion. For example, as shown in FIG. 10I,shield 32N according to a ninth modification may have a square shapehaving the same lengths both in the X axis direction and in the Y axisdirection, as viewed in the Z axis direction. Shield 32N according tothe ninth modification has a chamfered corner, as viewed in the Z axisdirection, and has a circumference that is at least partly formed of acurved line, as viewed in the Z axis direction. In this modification,chamfering area S may be calculated in the same manner as theembodiments mentioned above.

In each embodiment and each modification, each shield is rectangular.However, the shield may have a shape other than a rectangular shape aslong as the above-mentioned effect is obtained by removing unnecessarymagnetic domains at the end portion. For example, as shown in FIG. 10J,shield 32O according to a tenth modification may have a circle shapehaving the same lengths in the X axis direction and in the Y axisdirection, as viewed in the Z axis direction. Shield 32O according tothe tenth modification has a chamfered corner, as viewed in the Z axisdirection, and has a circumference that is at least partly formed of acurved line, as viewed in the Z axis direction. It should be noted thatchamfering area S of this modification is defined to be an area of theregion that is surrounded by a square that is surrounded by four linehaving a length that is equal to the diameter of shield 32O, or therectangular that is depicted with the dot-dash line in the figure andshield 32O.

It should be noted that the first to tenth modifications may also beapplied to yokes 32D, 32E etc. of the fourth and fifth embodiments.

In each embodiment, chamfering area S that is defined in the descriptionis S1 (μm²) or more and S2 (μm²) or less. Here, S1 is 1.0×10⁻³, and S2is 2.5×10. Instead of the above, for example, a distance betweenintersection IS (see FIG. 1D) and corner 36 on a normal line of corner36 that pass through intersection IS may be defined to be distance d, asviewed in the Z axis direction. Suppose that distance d that correspondsto chamfering area S1 (μm²) is distance d1 (μm) and distance d thatcorresponds to chamfering area S2 (μm²) is distance d2 (μm). Then, it ispossible to say in each embodiment and each modification that distance dshould be d1 (μm) or more and d2 (μm) or less. Distance d1 is 1.0×10⁻³,and distance d2 is 5.0.

In the fourth embodiment, each yoke 32D, 34D collects a magnetic fieldin the Y axis direction and guides the magnetic field that is collectedin the Y axis direction (see FIGS. 7A and 7B). In fifth embodiment, eachyoke 32E, 34E collects magnetic field in the Z axis direction and guidesthe magnetic field that is collected in the Y axis direction (see FIGS.9A and 9B). However, each yoke 32D, 34D and each yoke 32E, 34E maycollects a magnetic field in the X axis direction and guides themagnetic field that is collected in the X axis direction. It is needlessto say that an arrangement in which a magnetic field in a directionother than the fourth and fifth embodiments is collected and themagnetic field that is collected is guided in a different direction isincluded in the scope of the present invention.

In each embodiment, the spacer layer that constitutes element portion 20is a tunneling barrier layer, and element portion 20 is a TMR element.However, the spacer layer that constitutes element portion 20 may be anonmagnetic conductive layer that is formed of a nonmagnetic metal, suchas Cu, in order to form element portion 20 as a giant magnetoresistiveelement (GMR element). Element portion 20 may also be an anisotropicmagnetoresistive element (AMR element).

Each embodiment has been described by taking a position sensor as anexample. However, a magnetic sensor may be a sensor other than a positonsensor. For example, a magnetic sensor may be a compass that detectsterrestrial magnetism, an angle sensor, an encoder and so on.

It is needless to say that an embodiment in which one among theembodiments mentioned above, the modification thereof and the first tofourth modifications is combined with an element (or idea) of otherembodiments is included in the scope of the present invention.

Although certain preferred embodiments of the present invention havebeen shown and described in detail, it should be understood that variouschanges and modifications may be made without departing from the spiritor scope of the appended claims.

What is claimed is:
 1. A magnetic sensor comprising: a plurality ofmagnetoresistive elements each having a multi-layer structure; and aplurality of pairs of soft magnetic bodies that shield a magnetic fieldthat is applied to the magnetoresistive elements, wherein each softmagnetic body includes two pairs of straight sides and at least onesloping side, which is located between two adjacent ones of the straightsides, such that the sloping side is sloped with respect to each of theadjacent ones of the straight sides, as viewed in a stacking directionof the multi-layer structure of the magnetoresistive element, eachmagnetoresistive element has a magnetically sensitive axis along which achange in magnetic field is detected, and the magnetoresistive elementsare arranged in a direction perpendicular both to the magneticallysensitive axis and to the stacking direction, and each pair of the softmagnetic bodies is arranged to face opposite sides of a correspondingone of the magnetoresistive elements in the stacking direction and suchthat the pairs of soft magnetic bodies are arranged in the directionperpendicular both to the magnetically sensitive axis and to thestacking direction.
 2. The magnetic sensor according to claim 1, whereineach sloping side of the soft magnetic body is defined at leastpartially by a sloping line, as viewed in the stacking direction.
 3. Themagnetic sensor according to claim 1, wherein the sloping side isdefined only by a straight line, as viewed in the stacking direction. 4.The magnetic sensor according to claim 1, wherein the sloping side isdefined only by a curved line, as viewed in the stacking direction. 5.The magnetic sensor according to claim 1, wherein the sloping side isdefined by a combination of a curved line and a straight line, as viewedin the stacking direction.
 6. The magnetic sensor according to claim 5,wherein the sloping side is defined by the straight line and two curvedlines that are connected to opposite ends of the straight line,respectively, as viewed in the stacking direction.
 7. The magneticsensor according to claim 1, wherein a distance between an intersectionof an extension of a first one of the adjacent ones of the straightsides and an extension of a second one of the adjacent ones of thestraight sides and the sloping side is 1.0×10⁻³ (μm) or more and 5.0(μm) or less, as viewed in the stacking direction, and wherein the firstone of the adjacent ones of the straight sides forms a part of acircumference of the soft magnetic body and the second one of theadjacent ones of the straight sides forms another part of thecircumference and is inclined with regard to the first one of theadjacent ones of the straight sides.
 8. The magnetic sensor according toclaim 1, wherein each soft magnetic body includes an obtuse angle or acurved line on at least a part of a circumference thereof, as viewed inthe stacking direction.
 9. A magnetic sensor according to claim 1,wherein the magnetoresistive element exhibits a tunnelingmagnetoresistive effect.
 10. A magnetic sensor according to claim 1,wherein the magnetoresistive element exhibits a giant magnetoresistiveeffect.
 11. The magnetic sensor according to claim 1, wherein achamfering area formed by the sloping side is 1.0×10⁻³ (μm²) or more and2.5×10 (μm²) or less, as viewed in the stacking direction, wherein thechamfering area is defined by the sloping side and extensions of theadjacent ones of the straight sides.
 12. A magnetic sensor comprising: aplurality of magnetoresistive elements each having a multi-layerstructure; and a plurality of pairs of soft magnetic bodies that collecta magnetic field that is applied to the magnetoresistive elements,wherein each soft magnetic body includes two pairs of straight sides andat least one sloping side, which is located between two adjacent ones ofthe straight sides, such that the sloping side is sloped with respect toeach of the adjacent ones of the straight sides, as viewed in a stackingdirection of the multi-layer structure of the magnetoresistive element,each magnetoresistive element has a magnetically sensitive axis alongwhich a change in magnetic field is detected, and the magnetoresistiveelements are arranged in a direction perpendicular both to themagnetically sensitive axis and to the stacking direction, and each pairof the soft magnetic bodies is arranged such that one of the softmagnetic bodies is arranged on one side of a corresponding one of themagnetoresistive elements in the stacking direction and the other of thesoft magnetic bodies is arranged on an opposite side of thecorresponding one of the magnetoresistive elements in the stackingdirection and such that the pairs of the soft magnetic bodies arearranged in the direction perpendicular both to the magneticallysensitive axis and to the stacking direction.
 13. The magnetic sensoraccording to claim 12, wherein each sloping side of the soft magneticbody is defined at least partially by a sloping line, as viewed in thestacking direction.
 14. The magnetic sensor according to claim 12,wherein the sloping side is defined only by a straight line, as viewedin the stacking direction.
 15. The magnetic sensor according to claim12, wherein the sloping side is defined by a combination of a curvedline and a straight line, as viewed in the stacking direction.
 16. Themagnetic sensor according to claim 12, wherein a distance between anintersection and the sloping side is 1.0×10⁻³ (μm) or more and 5.0 (μm)or less, as viewed in the stacking direction, and wherein an extensionof a long one of the adjacent ones of the straight sides of the softmagnetic body and an extension of a short one of the adjacent ones ofthe straight sides of the soft magnetic body intersect at theintersection.
 17. The magnetic sensor according to claim 12, whereineach pair of the soft magnetic bodies is arranged to sandwich thecorresponding one of the magnetoresistive elements in a direction thatis inclined relative to the stacking direction.